1. Field of the Invention
The present invention relates to compositions for controlling the growth of microorganisms on a variety of substrates and in aqueous systems. More particularly, the invention relates to combinations of 2-(Thiocyanomethylthio)benzothiazole (TCMTB) with an N-alkyl heterocyclic compound and the use of such combinations as microbicides.
2. Background of the Invention
A large variety of commercial, industrial, agricultural, and wood materials or products are subject to microbiologicl attack or degradation which reduces or destroys their economic value. Examples of such materials or products include surface coatings, lumber, seeds, plants, leather and plastics. The various temperatures at which such materials or products are manufactured, stored, or used as well as their intrinsic characteristics make them susceptible to growth, attack, and degradation by common microorgansims such as algae, fungi, yeasts, and bacteria. These microorganisms may be introduced during a manufacturing or other industrial process, by exposure to air, tanks, pipes, equipment, and humans. They can also be introduced while using a material or product, for example, by multiple openings and reclosures of packages or from stirring or removing material with contaminated objects.
Aqueous systems are also highly subject to microbiological growth, attack, and degradation. The aqueous system may be a fresh, brackish or saltwater system. Exemplary aqueous systems include, but are not limited to, latexes, surfactants, dispersants, stabilizers, thickeners, adhesives, starches, waxes, proteins, emulsifying agents, cellulose products, metal working fluids, cooling water, waste water, aqueous emulsions, aqueous detergents, coating compositions, paint compositions, and resins formulated in aqueous solutions, emulsions or suspensions. These systems frequently contain relatively large amounts of water and organic material causing them to be environments well-suited for microbiologic growth and thus attack and degradation.
Microbiological degradation of aqueous systems may manifest itself as a variety of problems, such as loss of viscosity, gas formation, objectionable odors, decreased pH, emulsion breaking, color change, and gelling. Additionally, microbiological deterioration of aqueous systems can cause fouling of the related water-handling system, which may include cooling towers, pumps, heat exchangers, and pipelines, heating systems, scrubbing systems, and other similar systems.
Another objectionable phenomenon occurring in aqueous systems, particularly in aqueous industrial process fluids, is slime formation. Slime formation can occur in fresh, brackish or salt water systems. Slime consists of matted deposits of microorganisms, fibers and debris. It may be stringy, pasty, rubbery, tapioca-like, or hard, and may have a characteristic undesirable odor that is different from that of the aqueous system in which it formed. The microorganisms involved in its formation are primarily different species of spore-forming and nonspore-forming bacteria, particularly capsulated forms of bacteria which secrete gelatinous substances that envelop or encase the cells. Slime microorganisms also include filamentous bacteria, filamentous fungi of the mold type, yeast, and yeast-like organisms. Slime reduces yields in production and causes plugging, bulking, and other problems in industrial water systems.
Various chemicals known as industrial microbicides have been used to prevent microbiological deterioration of industrial systems, raw materials, and products. For instance, 2-(Thiocyanomethylthio)benzothiazole (TCMTB) is a well known, effective microbicide available for such uses. The use of TCMTB as an industrial microbicide has been described in U.S. Pat. Nos. 4,293,559, 4,866,081, 4,595,691, 4,944,892, 4,893,373, and 4,479,961. TCMTB is manufactured by Buckman Laboratories International Inc., and sold as Busan® 30L product, Busan® 30WB product, Busan® 1030 product, Busan® 1118 product as well as other products. TCMTB has the following chemical structure: 
Despite the existence of such microbicides, industry is constantly seeking more cost-effective technology which offers equal or better protection at lower cost and lower concentration. The concentration of conventional microbicides and the corresponding treatment costs for such use, can be relatively high. Important factors in the search for cost-effective microbicides include the duration of microbicidal effect, the ease of use, and the effectiveness of the microbicide per unit weight.